Well, with iOS 9, Apple took away the iOS 7 simulator that I would use to test this. The only way I could test with iOS 7 now is to buy a used iPad that still has iOS 7 on it. Apple really makes it difficult for developers to support old iOS versions.
I made some tweaks that might fix the problem in the next update, but I don't know if they will help. You can let me know, when that is available in the first week of January.
Alternatively, is there any reason you haven't updated beyond iOS 7? I've seen that iOS 9 causes some performance issues on older iPads, but an iPad Air should be fine.
If you do want to stay on an old iOS version, it's a good idea to keep all your apps at a comparable version. Running new app versions with an old iOS version or old app versions with a new iOS version are common sources of problems. Unfortunately, Apple doesn't provide a way to install earlier earlier app or iOS versions, so once you update one, you would need to update the other to bring them back into line.